Bkav fixes lock screen bypass flaw in Samsung phones

05:15:00 | 20-03-2013

Updated March 21: Bkav has just added a new function to its patch for Samsung lock screen flaw. Upon detecting illegal attempts to access the phone by exploiting ICE feature, Bkav Mobile Security will capture the unauthorized user's image with the phone's front camera, then email the photo to the phone's owner.

Mountain View, Calif., March 20, 2013 - A critical vulnerability on Samsung Galaxy Note II and Galaxy S III permits hackers to access the phone even when its screen has been locked. While Samsung has not been able to release a fix, today, Bkav Corporation successfully developed and integrated the patch into its free version of Bkav Mobile Security.

The vulnerability was first announced on March 4, permitting hackers to bypass the phone lock screen, no matter it is pattern lock, PIN, password, or face unlock mechanisms. Exploiting Samsung phone's ICE (In Case of Emergency) feature, combining with certain actions on home and power buttons, illegal users might access home screen of the phone, access apps like Contacts or Message, etc. without the owner's consent. Widgets like Calendar, Note… on the home screen (if any) might also be viewed.

Bkav has analyzed and found out that Samsung engineers have made logical mistake on programming ICE feature. Bringing ICE into use, Samsung has accidentally opened a path for deep access into its phones.

Essentially, home button is designed to get users back to home screen from the interface of any apps. All apps must comply with this rule. There is only one exception, that is when you are in emergency call window, pressing home will bring you to lock screen, not home screen. It is easy to understand! Emergency call is a special app which can be used even when the phone has been locked. Of course, after using this app, the phone must back to lock screen.

Meanwhile, ICE is just a normal application; hence like other apps on the phone, when ICE is running and users press home button, home screen will appear.

The flaw lies in the fact that Samsung engineers allow ICE to be launched from emergency call window. It means a normal app (in this case ICE) is allowed to run even when the phone has been locked.

As mentioned above, ICE is a normal app, if it is running and home button is pressed, home screen will appear. In other words, even when the screen has been locked, it is still possible to access home screen just by pressing home button as we all know.

While the official patch has not been released by Samsung, on March 11, Lookout – security firm – updated its Lookout Mobile Security software to protect users of Samsung Galaxy Note II and Samsung Galaxy S III against the bug.

Bkav experts have tested this feature of Lookout. Surprisingly, security firm Lookout seems to be following the failure of Samsung engineers.

On its blog, Lookout describes the technique used as follows: "…when Lookout detects the emergency contact dialer has been backgrounded, we preemptively bring it back to the forefront so that the rest of the phone cannot be accessed". From this description, Lookout uses ICE's status to detect attempts to bypass the phone's lock screen. If ICE is in background, it means ICE was running when home button was pressed, or somebody has just tried to exploit the lock screen flaw.

Lookout's approach to fix the bug is "bring it [ICE] back to the forefront" every time home button is pressed to pull ICE to background. "Ironically, this is also the failure road that Samsung engineers went on. Specifically, Samsung also tried to bring ICE back if it is backgrounded by home button. While, as we know, if a normal app (in this case ICE) is running when home button is pressed, the first and foremost occurrence must be home screen appearance. It means home screen has already been revealed, enough time for bad guys to access apps there. Then, even if Lookout succeeds in bringing ICE back, it is just the runner up to home screen", said Mr. Nguyen Minh Duc, Bkav Security Director.

Lookout fails to prevent lock screen bypass

Bkav's approach is to let Bkav Mobile Security block the calling of ICE to prevent the chance that a normal app (in this case ICE) is launched from the phone's lock screen, consequently prevent home screen to appear.

Bkav Mobile Security blocks the calling of ICE

Users can download the free version of Bkav Mobile Security from Google Play or from its developer's website Mobile.bkav.com. On the software's interface, choose Anti Theft, then tick on "Anti lock screen bypass". This option only appears in phones vulnerable to this bug (Galaxy Note II and S III).

About Bkav Mobile Security

Bkav Mobile Security is a software that protects your smartphone and now has more than 1 million users. Bkav Mobile Security is equipped with Smart Filter which automatically blocks up to 100% of SMS spams, the software blocks unexpected calls as well. Besides Antivirus, Anti Theft, Find my Phone, calls, messages, contacts Backup and Restore, Bkav Mobile Security is integrated with Privacy Advisor and Safe Browsing.